As others have said, NOT worth +$80/day. You can reserve the convertible class for less than that. I believe their code is CTAR, at least on this 2020 Miata RF barcode I saw at National/Ent/Alamo SFO a couple months ago:
https://i.imgur.com/opKd7wB.jpg
Didn't rent that car, but have had a Miata once before and it was super cramped and uncomfortable. I say that as a super lightweight and small person. I don't think 99% of Americans can breathe in a car like that.